N-linked oligosaccharides direct the differential assembly and secretion of inhibin alpha- and betaA-subunit dimers

Mol Endocrinol. 2007 Jul;21(7):1670-84. doi: 10.1210/me.2007-0050. Epub 2007 Apr 24.

Abstract

The biosynthetic pathway governing inhibin heterodimer (alpha/beta) and activin homodimer (beta/beta) assembly and secretion from ovarian granulosa cells is not fully understood. Here, we examined the role of inhibin subunit glycosylation in the assembly and secretion of mature inhibin A and activin A. Inhibition of subunit glycosylation by tunicamycin treatment of alpha- and beta(A)-expressing CHO cell lines reduced inhibin but not activin secretion. Dimeric inhibin A is preferentially secreted from parental isogenic wild-type (wt) cell lines (alpha(wt)beta(wt)). Mutation of a single glycosylation site at asparagine 268 (alpha(Delta268)beta(wt)) reduces inhibin secretion by 78% and permits beta/beta assembly and secretion. Conversely, gain of a glycosylation (GOG) site in the analogous region of the beta(A)-subunit (alpha(wt)beta(GOG327)) enhances inhibin A secretion. The present study demonstrates that N-linked glycan sites direct heterodimer vs. homodimer assembly, and prevention of glycosylation abrogates inhibin secretion. These data support a definitive role for site-specific N-glycosylation in governing inhibin/activin dimer assembly and secretion.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Activins / chemistry
  • Activins / genetics
  • Activins / metabolism
  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Binding Sites / genetics
  • CHO Cells
  • Cricetinae
  • Cricetulus
  • DNA Primers / genetics
  • Dimerization
  • Evolution, Molecular
  • Glycosylation
  • Inhibin-beta Subunits / chemistry*
  • Inhibin-beta Subunits / genetics
  • Inhibin-beta Subunits / metabolism*
  • Inhibins / chemistry*
  • Inhibins / genetics
  • Inhibins / metabolism*
  • Models, Biological
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Oligosaccharides / chemistry*
  • Oligosaccharides / genetics
  • Oligosaccharides / metabolism*
  • Protein Structure, Quaternary
  • Subcellular Fractions / metabolism
  • Transforming Growth Factor beta / antagonists & inhibitors
  • Tunicamycin / pharmacology

Substances

  • DNA Primers
  • Oligosaccharides
  • Transforming Growth Factor beta
  • activin A
  • inhibin beta A subunit
  • inhibin-alpha subunit
  • Activins
  • Tunicamycin
  • Inhibins
  • Inhibin-beta Subunits